Correlation between surface hydrophobicity changes and surface activity changes of soybean protein isolates caused by structural changes

The present work aimed to examine the association between the changes in the surface hydrophobicity and surface activity of soybean protein isolate (SPI) following structural alterations. To this end, the effects of heating, pH modification, ultrasonication, surfactant (SDS, sodium dodecyl sulphate) treatment, alkaline protease hydrolysis, peracetic acid treatment, and acylation on the surface activity and surface hydrophobicity of SPI were investigated. The results demonstrated that the changes in the surface hydrophobicity of SPI could accurately reflect the changes in its surface activity. A strong correlation between surface hydrophobicity and surface activity alterations was noted after the SPI molecules underwent structural modifications. The higher the surface hydrophobicity of the treated SPI, the greater its surface activity. Given that the surface hydrophobicity of SPI reflects the actual distribution of hydrophobic residues on its surface, this parameter can serve as a key indicator for evaluating and predicting changes in the surface activity of SPI.